OK, I'm struggling a bit and have given up trying to figure this out. I downloaded a .kml here: http: //www. wikitrail. org /sections /view/ at /3034 /dalton -to -bennington (obviously you need to take the spaces out of the link, for some reason it wouldn't let me post?)
When importing into Google Earth, it has both a trail/route/path whatever you would call it (part of the problem with GPSrs, GIS and other geospatial tech is that one firms term doesn't align with others, making things problematic.)
What shows on GE is exactly what appears on the above website. A line and some waypoints. I also converted it to .gpx online and imported it into Basemap. Again, in Basemap I get the waypoints and a track (footprint icon). And when I clicked on the location on the unit, it shows the trail in BC. The only place the trail does not appear is on the actual unit despite it clearly being loaded.
However, and this is the perplexing problem, when I send the .gpx file to to my Oregon, the trail/route/track does not appear. However, in the GPX folder, there is a new Track and Waypoint file. So it's odd that the track does not appear.
UPDATE - OK so the issues is, the trail I downloaded was a Track and is in the Track Manager. Can I convert that to some file that makes it a permanent trail feature on the unit's main map?
Have a look at GPSU (www.gpsu.co.uk) - there is a function to convert tracks (with thousands of points) to routes (with tens of points)
You cannot modify "the unit's main map". You can create your own maps however, and there are tutorials on this site to show you how. This gets very complex and technical though, not something an ordinary user would want to do.
Converting a track to a route might work, but that may over-simplify the original file. You could try this simple program which turns tracks into maps without all the complexity of building a full map with traditional tools. The maps that it creates are transparent, so you can enable them at the same time as another map and the tracks will be added to it.
http://www.javawa.nl/imgfromgpx_en.html
(Caveat: have never tried this myself... I use the "very complex and technical" method to make maps ;D )